The peripheral surface of a roll is covered with a tube-shaped film made of fluorine resin or fluorine resin containing carbon black which is conductive. The roll includes rolls for use in a printing machine, a rolling machine, and a drier; and a fixing heating roll, a fixing pressurizing roll, an electrostatic charging roll, a cleaning roll, a developing roll, a transfer roll for use in a copying machine, a printer, and a facsimile of electrophotographic type.
Generally, fluorine resin is superior to resin made of other substances in water repellency, oil repellency, slidableness, stain-proofing property, heat-resistant property, chemical-resistant property, and electrical characteristic. Thus, fluorine resin is widely used. Because the surface of the fluorine resin is inert, it is difficult to apply adhesive agent or paint thereto and thus it is difficult to combine fluorine resin with other materials. Various treating methods have been hitherto proposed to allow surface of fluorine resin to be adhesive or wettable. As a known art for treating the inner peripheral surface of a very thin film tube, one end of a film tube is closed and surface-treating liquid is injected from its other end which is open to stay the surface-treating liquid above the closed one end, as disclosed in Laid-Open Japanese Patent Publication No. 5-59195. As another known art, the outer peripheral surface of a film tube is treated with liquid chemical and then, the tube is cut to a plurality of predetermined lengths, and each tube is turned inside out by using a jig to obtain a tube-shaped film whose inner peripheral surface is treated, as disclosed Laid-Open Japanese Patent Publication No. 5-86222.
In the above-described conventional treating methods, liquid chemical is applied to the inner peripheral surface of the tube-shaped film. According to the disclosure made in Laid-Open Japanese Patent Publication No. 5-339396, in order to allow the surface of fluorine resin to be adhesive and wettable, after a light-absorbing substance is attached to the surface thereof, the surface is irradiated with ultraviolet laser beams. Effective methods of treating the surface of the tube-shaped film by applying liquid chemical thereto have been established as described above, whereas effective methods of treating the surface of the tube-shaped film by irradiating the surface with optical energy such as ultraviolet laser beams have not been established.
In the conventional treating methods disclosed in Laid-Open Japanese Patent Publication Nos. 5-59195 and 5-86222, folds are formed in the tube-shaped film. That is, the conventional treating methods are incapable of providing the tube-shaped film having no folds generated on the entire surface of the inner peripheral surface thereof. More specifically, in the method disclosed in Laid-Open Japanese Patent Publication No. 5-59195, the tube is sandwiched under pressure between a pair of pinch rollers. As a result, a striped fold is formed at the portion grasped with the pinch rollers. In the method disclosed in Laid-Open Japanese Patent Publication No. 5-86222, in dipping the tube-shaped film in a tank containing liquid chemical, the rolled film is unrolled to feed it along a guide roller with the film sandwiched between the pinch rollers and the guide roller. That is, because the film is rolled on a roller by making the cylindrical configuration into a flat configuration, folds are formed therein.